The Collaborative International Dictionary
circuit breaker \cir"cuit break"er\, n. (Elec.) A device contained within an electrical circuit designed to interrupt the circuit when the current exceeds a preset value; it is sometimes called a contact breaker. Its function is to prevent fire or damage to the circuit or the devices on the circuit which could be caused by excess current, such as that caused by a short-circuit. It differs from a fuse in not having a conducting element which melts (see 2nd fuse, n.). Circuit breakers are designed to be easily reset, i. e. to reclose the circuit after it has been opened by the circuit breaker; this is usually accomplished by simply moving a switch back and forth. They are commonly used in buildings to protect individual electrical lines, and are often contained in groups within a box called a circuit breaker panel, which divides the current from a main electrical line into multiple circuits each protected by a separate circuit breaker. Less commonly they may be found on individual devices.
Wikipedia
A contact breaker (or "points") is a type of electrical switch, and the term typically refers to the switching device found in the distributor of the ignition systems of spark-ignition internal combustion engines.
Usage examples of "contact breaker".
The terrorist reached up, opened the box, and pulled the contact breaker downward.
It was like when you're counting on an aircraft being finished for the morning flight to Khartoum, and an engineer comes up at six o'clock in the evening and tells you he needs a right-hand contact breaker and they've only got left-hand ones in the store and they've been telephoning all round and there aren't any right-hand ones in Cairo.
They had dismantled the magneto in the engine room and discovered that all that it required was a new contact breaker.